As an oxidizer for composite solid propellant, ammonium perchlorate (henceforth to be called AP) has been widely and generally used in the past because of its high performance. Although AP has been used for a long time and is one of the most popular oxidizers, it poses a problem for its use that it generates smoke as exhaust gas. Therefore, research workers of this country and outside have been endeavoring to find out oxidizers which do not pose any of the said problem and have the equal performance as AP. And one of these oxidizers is ADN. ADN is a compound consisting of nitrogen, hydrogen and oxygen, is clean as to exhaust gas and is a high energetic material. Hence, as a substitute of AP which is currently in use, it is the most suitable oxidizer to improve the performance of solid fuel rocket while harmonizing with environment. Having noticed its characteristics, the developed countries of America and Europe are actively engaging in the development of ADN. As to the development of ADN, Russia is more advanced than any other countries since the former Soviet Union. Although it has been reported that Russia has been producing ADN in the scale of several hundreds of tons, the details are entirely unknown. The United States of America has been also engaging in ADN research development with a combined effort of the government and private enterprise, and a part of the achievements has been disclosed through its patent applications.
It has been known to be the year of 1971 that potassium salt of dinitramide was synthesized. Since then there have been developed some prior arts on the method of forming dinitramide salts, especially ammonium salt (ADN).
First, there is the art of National Publication of Translated Version 5-500795(PCT/US91/04268). This is a method for nitrating nitramide. This reaction can be represented by the chemical equations of (I) and (II). ##STR1##
This method starts with forming nitrourethane by the nitration of urethane wherein the nitration reagent is ethyl nitrate, or fuming nitric acid in combination with acetic anhydride. Further, this product is reacted to form an ammonium salt and then form a potassium salt, and finally results in nitramide. This process of forming nitramide involves many steps and is complicated; moreover, potassium salt and nitramide are so unstable that they are not easy to handle; in addition to these, nitramide is produced with a very low yield based on the amount of the starting material, urethane; and further to obtain ADN nitramide is to be nitrated. Hence, it is not considered to be a suitable method for forming ADN.
Then, there is another prior art of W093/16002. This is a method based on the direct nitration of ammonium nitrourethane. ##STR2##
This method may be called an improved type of the aforementioned National Publication of Translated Version 5-500795(PCT/US91/04268). That is, this is the method of forming ADN directly form ammonium nitrourethane(NO.sub.2 NCOOC.sub.2 H.sub.5.NH.sub.4), which is an intermediate product obtained in the process of the aforementioned National Publication of Translated Version 5-500795(PCT/US91/04268). It is regarded to be a more reasonable method since the object product is formed without isolating the unstable nitrourethane potassium salt (NO.sub.2 NKCOO.K) and nitramide (NO.sub.2 NH.sub.2). However, this method still requires considerable steps to produce ammonium nitrourethane.
To resolve the above matter, another prior art of W091/19669 has been employed to obtain ADN by decomposing a special dinitramine with ammonia or other compound. This reaction can be represented by the following general chemical equation (IV). EQU L.sub.n ZR.sup.- N(NO.sub.2).sub.2 +MX--.fwdarw.MN(NO.sub.2).sub.2 +L.sub.n ZX+R (IV)
where
L is the same or different 1-6 carbon alkyl, arlyl, hydrogen, halogen, or other group; PA1 n is 1 to 3; PA1 Z is an element of Si, Sn, Ge, As, B, Bi, Sb, Pb, or Hg; PA1 R.sup.- is a 1 to 6 carbon alkylene group; PA1 R is an alkyl group; PA1 M.sup.+ ion is either a metal cation, an ammonium cation, or a hydrazinium cation; and PA1 .sup.- X ion is an anion of either F, Cl, OH, CO.sub.3, or COR. PA1 (b) a process for the formation of nitrourea by reacting the urea nitrate with sulfuric acid; PA1 (c) a process of reacting the nitrourea with a nitration reagent such as nitronium tetrafluoroborate, and then adding ammonia gas to the reaction mixture; and PA1 (d) a process of filtering off the resulting byproduct of crystals, concentrating its filtrate, adding ethyl acetate to this concentrated filtrate, filtering off the precipitate, concentrating again its filtrate under vacuum, and finally separating ADN as crystals by adding chloroform to the concentrated filtrate.
An example of the above-mentioned dinitramine is (CH.sub.3).sub.3 SiCH.sub.2 N(NO.sub.2).sub.2. However, in order to obtain this kind of dinitramine the reaction is to be carried out from the corresponding isocyanate as shown in the following chemical equation. ##STR3##
If the above reaction is employed, it is certain that the product will be very expensive. Even if the reaction is carried out by decomposing a comparatively simpler dinitramine of L.sub.n ZR.sup.-, for example CNCH.sub.2 CH.sub.2 N(NO.sub.2).sub.2, with ammonia, the synthetic process is still complicated.